Biofuels via hydrogenolysis and dehydrogenation-condensation

Abstract

A method comprising providing a carbohydrate feed; contacting at least a portion of the carbohydrate feed directly with hydrogen in the presence of a hydrogenolysis catalyst to produce a first reaction product comprising a stable hydroxyl intermediate; contacting at least a portion of the first reaction product comprising the stably hydroxyl intermediates with a dehydrogenation catalyst to form a second reaction product; and contacting at least a portion of the second reaction product with a condensation catalyst comprising a base functionality to form a fuel blend.

Description

[0001]The present application claims the benefit of pending U.S. Provisional Patent Application Ser. No. 61 / 333,916, filed May 12, 2010 the entire disclosure of which is hereby incorporated by reference.FIELD OF THE INVENTION[0002]The invention relates to the production of higher hydrocarbons suitable for use in transportation fuels and industrial chemicals from bio-based feedstocks.BACKGROUND OF THE INVENTION[0003]A significant amount of effort has been placed on developing new methods and systems for providing energy from resources other than fossil fuels. Bio-based feedstocks are a resource that show promise as a renewable alternative source of hydrocarbons for producing fuel and chemicals.[0004]Bio-based feedstocks including carbohydrates and “biomass” are materials derived from living or recently living biological materials. One type of biomass is cellulosic biomass. Cellulosic biomass is the most abundant source of carbohydrate in the world due to the lignocellulosic materials...

AI Technical Summary

Benefits of technology

[0021]The methods and systems of the invention have the advantage of converting bio-based feedstocks, optionally without any additional costly purification steps to form higher energy density product of lower oxygen / carbon ratio including higher alkanes, olefins, and aromatics. The invention also reduces the amount of unwanted byproducts, thereby improving the overall yield of converting carbohydrates to higher hydrocarbons. Another advantage of the present invention includes the use of similar catalysts for multiple reaction steps, offering the potential to combine reactions when desired. A further advantage of the present invention provides the combination or elimination of steps required to convert bio-based feedstocks to fuel, thereby reducing capital costs. While not intending to be limited by theory, it is believed that some carbohydrates may thermally degrade at the conditions needed to produce higher hydrocarbons. In addition, the inclusion of some higher polyols in a reaction to form high hydrocarbons may result in excessive condensation so that the resulting higher hydrocarbons are unusable for transportation fuels (e.g., tars). As an advantage of the present process, the hydrogenolysis reaction may allow for the formation of stable hydroxyl intermediates that can withstand the conditions needed to form higher hydrocarbons and allow for the formation of desired higher hydrocarbons that may be used for fuels or as other industrial chemicals. Advantages of specific embodiments will be described in more detail below.

[0022]An embodiment of the invention comprises providing a carbohydrate feed; contacting at least a portion of the carbohydrate feed directly with hydrogen in the presence of a hydrogenolysis catalyst to produce a first reaction product comprising stable hydroxyl intermediates; contacting at least a portion of the first reaction product comprising the stable hydroxyl intermediates with a dehydrogenation catalyst to form a second reaction product; and contacting at least a portion of the second reaction product with a condensation catalyst comprising a base functionality to form a fuel blend.

[0023]Carbohydrates are the most abundant, naturally occurring biomolecules. Plant materials store carbohydrates either as sugars, starches, celluloses, lignocelluloses, hemicelluloses, and any combination thereof. In one embodiment, the carbohydrates include monosaccharides, polysaccharides or mixtures of monosaccharides and polysaccharides. As used herein, the term “monosaccharides” refers to hydroxy aldehydes or hydroxy ketones that cannot be hydrolyzed to smaller units. Examples of monosaccharides include, but are not limited to, dextrose, glucose, fructose and galactose. As used herein, the term “polysaccharides” refers to saccharides comprising two or more monosaccharide units. Examples of polysaccharides include, but are not limited to, sucrose, maltose, cellobiose, cellulose and lactose. Carbohydrates are produced during photosynthesis, a process in which carbon dioxide is converted into organic compounds as a way to store energy. The carbohydrates are highly reactive compounds that can be easily oxidized to generate energy, carbon dioxide, and water. The presence of oxygen in the molecular structure of carbohydrates contributes to the reactivity of the compound. Water soluble carbohydrates react with hydrogen over catalyst(s) to generate stable hydroxyl intermediates comprising polyols and sugar alcohols, either by hydrogenation, hydrogenolysis or both.

[0024]In the embodiment shown in FIG. 1, the carbohydrates are optionally reacted in a hydrogenation reaction and then a hydrogenolysis reaction to form suitable stable hydroxyl intermediates that comprise alcohols and polyols for the condensation reaction 110. In an embodiment of the invention, the hydrogenation reaction is optional and the hydrogenolysis reaction alone is suitable to form the desired stable hydroxyl intermediates. In another embodiment of the invention, the carbohydrates are passed through the hydrogenolysis reaction prior to being passed through the hydrogenation reaction (thus hydrogenolysis reaction 106 and hydrogenation reaction 104 are reversed from the order shown in FIG. 1). In an embodiment of the invention, the hydrogenation and hydrogenolysis reactions occur in the same vessel to generate stable hydroxyl intermediates to be fed into a processing reaction. In an embodiment, a separation step (e.g., water removal) could be conducted prior to the hydrogenolysis reaction.

[0025]The carbohydrates may originate from any suitable source. In an embodiment, the carbohydrates fed to the process may be derived from an organic source (e.g., sugars and starches from corn or sugarcane). In another embodiment, the carbohydrates are derived from bio-based feedstocks. Bio-based feedstocks can include biomass. As used herein, the term “biomass” means organic materials produced by plants (e.g., leaves, roots, seeds and stalks), and microbial and animal metabolic wastes. Common sources of biomass include: agricultural wastes (e.g., corn stalks, straw, seed hulls, sugarcane leavings, bagasse, nutshells, and manure from cattle, poultry, and hogs); wood materials (e.g., wood or bark, sawdust, timber slash, and mill scrap); municipal waste, (e.g., waste paper and yard clippings); and energy crops, (e.g., poplars, willows, switch grass, alfalfa, prairie bluestream, corn, and soybean). The term “biomass” also refers to the primary building blocks of all the above, including, but not limited to, saccharides, lignins, celluloses, hemicelluloses, and starches. Useful carbohydrates in the invention include, but are not limited to, carbohydrates that can be converted to hydrocarbons under suitable reaction conditions. Suitable carbohydrates in the invention include any carbohydrate soluble in water or an organic solvent having one or more carbon atoms and at least one oxygen atom. The carbohydrates may also have an oxygen to carbon ratio from about 0.5:1 to about 1:1.2.

[0026]In one embodiment of the invention, the bio-based feedstock is optionally first hydrolyzed in a liquid medium such as an aqueous solution or aqueous solution with organic solvent (e.g., a recycled portion of the stable hydroxyl intermediates), to obtain a soluble carbohydrate stream for use in the process. Various biomass hydrolysis methods may be suitable, including, but not limited to, acid hydrolysis, alkaline hydrolysis, enzymatic hydrolysis, and hydrolysis using hot-compressed water. In certain embodiments, the hydrolysis reaction can occur at a temperature between 100° C. and 250° C. and pressure between 0.1 MPa and 10,000 kPa. In embodiments including strong acid and enzymatic hydrolysis, the hydrolysis reaction can occur at temperatures as low as ambient temperature and pressure between 100 kPa and 10,000 kPa. In some embodiments, the hydrolysis reaction may comprise a hydrolysis catalyst (e.g., a metal or acid catalyst) to aid in the hydrolysis reaction. The hydrolysis catalyst can be any catalyst capable of effecting a hydrolysis reaction. For example, suitable hydrolysis catalysts include, but are not limited to, acid catalysts, base catalysts, metal catalysts, and any combination thereof. Acid catalysts can include organic acids such as acetic acid, formic acid, and levulinic acid. In an embodiment, the acid catalyst can be generated as a byproduct during the hydrogenation and / or hydrogenolysis reactions. In certain embodiments, the hydrolysis of the bio-based feestocks can occur in conjunction with the hydrogenation and / or hydrogenolysis reactions. In such embodiments, a co-catalyst or catalytic support may be added to the hydrogenation and / or hydrogenolysis reactions to facilitate the hydrolysis reaction.

Problems solved by technology

For example, the processes used are costly and complex making it difficult to compete with the use of traditional resources, such as fossil fuels.

The conversion of carbohydrates to hydrocarbons in this system results in increased loss of desirable hydrocarbon products due to the formation of unwanted byproducts, such as coke, carbon dioxide, and carbon monoxide.

Thus, another challenge for promoting and sustaining the use of biomass is the need to eliminate the formation of undesirable byproducts such as carbon monoxide, carbon dioxide, and coke.

A further challenge is to complete the conversion of carbohydrates to higher hydrocarbons in a limited number of steps, to obtain high yields with minimal capital investment.

However, ethanol does not have a high energy density when compared to standard transportation fuels.

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